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Campus-Only Access for Five (5) Years
Doctor of Philosophy (PhD)
Year Degree Awarded
Month Degree Awarded
Copper (Cu)-based pesticides have been widely used as a broad-spectrum
management strategy in agriculture over the past century. However, extensive
applications of conventional Cu-based pesticides over years can lead to Cu pollution and
raise risks at the un-targeted organisms in the environment. A novel and sustainable
strategy for improving the antimicrobial efficiency of pesticides while simultaneously
minimizing their negative impacts on ecosystems is needed. Thus, this dissertation
describes three main objectives to comprehensively understand the transformation of Cubased
nanoparticles (NPs) as affected by root exudates in the rhizosphere, antifungal
activity of newly developed Cu-based NPs, and their roles in the enhancement of nutrient
uptake, metabolite regulation, and plant growth.
1) The effects of maize (Zea mays L.)-derived root exudates (RE) and their
components on the aggregation and dissolution of copper oxide (CuO) NPs in the
rhizosphere were investigated. In this work, RE significantly inhibited the aggregation of
CuO NPs regardless of ionic strength and electrolyte type. Furthermore, this inhibition
was correlated with the molecular weight (MW) of RE fractions. Higher MW fraction
(>10 kDa) reduced the aggregation most. We also discovered that RE significantly
promoted the dissolution of CuO NPs and lower MW fraction (< 3 kDa) RE mainly
contributed to this process. The addition of 20 mg/L RE reduced the seedlings’ growth
rate to 1.89% after 7 days of exposure to 25 mg/L CuO NPs, which were significantly
lower than the control group (4.82%). Notably, Cu accumulation in plant root tissues was
significantly enhanced by 20 mg/L RE. This study provides useful insights into the
interactions between RE and CuO NPs, which is of significance for the safe use of CuO
NPs-based antimicrobial products in agricultural production.
2) To increase the antifungal efficacy against the pathogenic activity of
Gibberella fujikuroi (bakanae disease) in rice (Oryza sativa L.), we synthesized copper
sulfide (CuS) NPs at 1: 1 and 1: 4 ratios of Cu and S, and treated infected rice (Oryza
sativa L.) with CuS NPs by foliar application and seed treatment. The results showed that
treating with both types of CuS NPs at 50 mg/L at the seed stage significantly decreased
disease incidence on rice by 35.1 and 45.9%, respectively. Comparatively, CuO NPs
achieved only 8.1% disease reduction, and the commercial Cu-based pesticide Kocide
3000 had no impact on disease. Foliar-applied CuO NPs and CuS (1: 1) NPs decreased
disease incidence by 30.0 and 32.5%, respectively, which outperformed CuS (1: 4) NPs
(15%) and Kocide 3000 (12.5%). Notably, CuS (1: 4) NPs also modulated the shoot
salicylic acid (SA) and jasmonic acid (JA) production to enhance the plant defense
mechanisms against G. fujikuroi infection.
3) The third study was aimed to investigate the effectiveness of a controlled
release Cu-based nano-agrichemicals in control Fusarium oxysporum f. sp. lactucae (F.o.
lact) infection on lettuce and explore their roles in the enhancement of nutrient uptake,
metabolite regulation, and plant growth. Our study demonstrated that as compared to
commercial CuO NPs, the synthesized CuO NP-embedded hydrogels at 31 mg Cu/kg soil
and 145 mg dried hydrogel powder/kg soil had a controlled release of Cu ions that could
markedly reduce the required amounts of active components (e.g., Cu in this case).
Additionally, compared to Kocide 3000 and CuO NPs, the synthesized CuO NPembedded
hydrogels exhibited greater disease suppressing activity against F.o. lact.
Notably, CuO NP-embedded hydrogels enhanced uptake of P, Mn, Zn, and Mg, and also
increased the shoot levels of organic acids as compared to the diseased control. Increased
SA but lowered levels of JA and abscisic acid (ABA) in shoots enhanced disease
Shang, Heping, "Fate and Application of Copper-based Nanoparticles in Agriculture" (2021). Doctoral Dissertations. 2344.
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